Preheat the oven to 350 degrees. Grease a 9x5 inch loaf pan.
In a large bowl, combine the butter and sugar. Next, add in the eggs and vanilla. Mix well.
In a separate bowl, combine the flour, salt, and baking soda. Add these dry ingredients to the butter mixture. Combine well.
Fold in the sour cream, walnuts, and bananas until it is incorporated. Spread evenly into the prepared pan.
Bake at 350 degrees for 60 minutes, or until a toothpick comes out clean when inserted into the center of the pan.
Cool loaf in pan for 5 minutes and then transfer the loaf out of the pan and onto a cooling rack to cool completely.
